Application Note 1164 LM3647 Reference Design User`s Manual
Contents
1. C B 3988 If an NTC with different characteristics is used then the resistor R28 may need to be changed The charger uses voltage levels to trigger under over temperature conditions The voltage at the temperature inoput must be between 2 2V or 0 5V for the charger to start During charging the voltage must stay between 3 0V for Li lon or 3 15V for Ni Cd Ni MH and 0 5V or the charger will register a temperature fault and abort the charge Ta lve we J3 J8 AN101315 15 Voltage at Temperature input 10 5 0 5 10 15 20 25 30 35 40 45 50 Temperature in C AN101315 16 The three jumpers J2 J5 and J6 are connected to the three selection pins SEL1 SEL2 and SEL3 These jumpers are used to select how the charger should behave see Charger Modes table PWM Timeout O0Od0O oa T J7 D6 D4 D3 LM3647 L C2 E LIFE SUPPORT POLICY Buzzer 317 resistor lt O O000000 OOOO000 OO00000 DOOOO0O0 Battery Current oooogy9jo0oo0oo0o0g0 J153 O0O000 O0000 O J15 Discharge resistor Q2 AN101315 17 NATIONAL S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or systems which a are intended for surgical implant into the body or b support or sustain life and who2. for Ni Cd Ni MH only slow PWM mode This mode uses an external constant current power source which is switched on and off according to the charge phase of the LM3647 The frequency is approximately 0 1 Hz The advantage of this charge method is that operational amplifiers and the current feedback circuitry are not needed which provides a low cost solution The dimensioning of the voltage divider network is performed the same way The constant current source is dimensioned in the following manner 1 25 V4 lout gt a Vy Voltage drop across D1 UNREGULATED_DC L gt V_OUT SLOW_PWM L_ AN101315 7 The LM3647 regulates the constant current source by turning the transistor Q1 on and off When the transistor is off the LM317T regulator feeds a constant current to the battery at V_OUT When the transistor is on the output from the LM317 is limited to 1 25V which should be greater than the battery voltage Charge Phase Duty Cycle Fast Charge 100 Topping Charge Maintenance Charge www national com VOLL NV AN 1164 2 0 APPLICATION INFORMATION 2 1 Typical Example 2 1 1 Ni Cd Ni MH 5V 5V ee 10 100 nF 22 nF 3i 4 L gt SEL4 be c5 c6 229 R4 100k 5V 5V 5V an Qt pee PSS P i R18 am a 3 3k S py py BUZZER 23 vns351 R1 R16 R17 330 330 SEL3 SEL4 RCIN GND 5V RESET LED1 ZJ TEMPERATURE LED2 R5 Wee i 3 3k CON SIP 2P TEMPERATURE R6 1 5K CON SIP 2P s G D
3. when the CEL pin gt 1 0V The charger can also detect a battery that has been deeply discharged and does not have any voltage across the battery terminals This is accomplished by applying a small pre charge current once every minute for up to 15 seconds The deeply discharged battery will accept this charge and the battery potential will eventually rise above the 1 0V limit to initiate normal charging When the charger has detected a battery CEL pin gt 1 0V it checks to see if the temperature is within range to start charging If itis then it applies a small current of 0 2C for approximately 1 minute If the battery voltage is close to fully charged the charger will not reach the charging voltage within 1 minute and the charge process will restart This occurs only with batteries that are already fully charged and consequently should not be recharged If the battery voltage has not reached the Li lon battery qualification voltage CEL pin gt 1 2V within 1 minute of the Qualification Phase the battery is considered to be defective and the charger goes into error mode It stays there until the battery is removed CEL pin lt 1 0V The next phase is Fast Charge Constant Current During this phase the current is constant and the battery voltage will slowly rise due to the charging When the battery has reached its maximum battery voltage CEL at 2 675V or 2 74V depending on SEL3 it will go to the next phase which is Fas
4. C voltage and deliver enough current to drive the circuitry all LED s buzzer LM3647 e The transistor Q3 must be able to handle the charge current and depending on charge current must be provided with an adequate heatsink e The transistor Q2 must be able to handle the maximum discharge current The Diode D1 must be able to handle the maximum charge current 1 2 2 2 Clarifications Regarding Circuit Schematics The circuitry with Q4 R26 and R27 see section below is used to protect the battery from excessive charge current When the current flows through the current sense resistor R9 and is amplified by U2 the voltage at U2 s output drops from 2 5V until Q4 starts conducting It discharges the RC network that generates the DC voltage from the PWM output of the LM3647 1 2 2 3 Setting The Charge Timeout The LM3647 uses the charge timeout value as a backup termination method if the normal termination methods fail The charge timeout also controls the length of some of the phases like the Topping Charge phase Ni Cd Ni MH The timeout is selectable from a charge rate of 3 2C to 0 4C The table below shows which values will result in a certain timeout TABLE 1 Charge Timeouts Ni Cd Ni MH Fast Charge minutes Ni Cd Ni MH Topping minutes R Value 100 kQ 100 kQ 100 kQ 100 kQ 100 kQ 100 kQ 100 kQ 100 kQ EXAMPLE 1 NiMH Battery Pack Capacity 800 mAh Charge Current 600 mA 600 mA Charge Rat
5. ISCHARGE C gt A AN101315 8 Ve No eDseiaige before Charge Fast PWM LM3647 has current feedback Discharge before Charge a E Maintenance Charge Only Slow PWM external current control www national com 6 2 1 2 Li lon 5V 5V UNREGULATED_DC MAX20V Ta IC2 TIP121 D1 10 100nF 22nF fy 8 c E gt SEL4 rae wa a GND 6 C7 4 5 6V NC NC c6 R23 1 pF 100 u 100k LM78L05S0 5V 5V 5V BUZZER Ne ai Lu to nn Q3 NDS351 m goal al Lo Lo nn y R14 rte R17 330 330 330 2 c3 8 2 pF fea SEL3 seL2 0 1 R9 gt UNREGULATED_DC l 0 047 X X 5V 2 SYSOKH vaxz20v 4 DISCHG DISCHARGE TENP HH TEMPERATURE _R19 WL 4 cS CONRA 2P R21 y 5V CONRA 2P p 2 C4 R2 A 5V 68k m ae BAS16LT1 NC 10 uF 7 r TEMPERATURE C en DISCHARGE L gt R3 7 DS 100k 33k T LM4040A 2 5 A AN101315 9 SEL1 After charging maintenance charging until battery removal 4 2V Cell After charging maintenance charging until battery removal If battery Li lon NA voltage drops below a predefined value the charger restarts the charge process GND After charging no maintenance charging is applied If battery voltage NA 4 1V Cell drops below a predefined value the charger restarts the charge process Note When a three chemistry charger is designed special considerations must be taken into account regarding configuration pin SEL3 this pin has differnet meanings when switching
6. LM3647 Reference Design User s Manual GENERAL DESCRIPTION The LM3647 is a charge controller for Nickel Cadmium Ni Cd Nickel Metal Hydride Ni MH or Lithium lon Li lon batteries The device uses a pulsed current charging or a constant current charging technique The device can also be configured to discharge before charging Throughout the charging sequence the LM3647 monitors voltage and or temperature and time in order to terminate charging e Negative delta voltage AV e Maximum voltage e Optional Delta temperature delta time AT At e Optional Maximum temperature e Backup Maximum time The LM3647 is user configurable for three battery chemistries Ni Cd Ni MH or Li lon In Ni Cd Ni MH mode four different charging phases are used e Softstart charge e Fast charge e Topping charge e Maintenance charge In Li lon mode four different charging stages are used e Qualification e Fast Charge Phase 1 Constant Current e Fast Charge phase 2 Constant Voltage e Maintenance charge KEY FEATURES e Auto adaptive fast charge e High resolution accurate voltage monitoring prevents Li lon under charge or overcharge e Fast charge pre charge and maintenance currents are provided Different currents are selectable via external resistors e Fast charge termination by temperature time maximum voltage maximum temperature and maximum time e Dynamically detects battery insertion removal short circuit and bad bat
7. between Ni Cd Ni MH and Li lon To ensure correct operation the SEL3 pin MUST be tied to VCC If Li lon cells of 4 1V Cells is used then minor adjustments have to be done to the voltage measurement resistor divider 7 www national com VOLL NV AN 1164 3 0 LM3647 REFERENCE DESIGN DEMO BOARD The demo board provides a combined multi chemistry solution with hardware for both external constant current source and LM3647 controlled charge current Located near the top left corner of the board is the power supply connector next to the heatsink When using the external constant current source a power resistor needs to be connected at the connector marked 317 resistor The values of the resistor can be calculated using the equation 4 mentioned earlier At the bottom right corner of the board are two connectors that lead to the battery and discharge resistor The value of the discharge resistor depends on the battery pack voltage and the maximum discharge rate The demo board has different jumpers that are assigned to different setups Some of the components are not populated providing support for user specific values The timeout jumper J18 is used to select different timeouts from 2 4C to 0 4C The values mounted on the demo board result in timeouts corresponding to the charge rates shown below OOOO LOM Nw oO N AN101315 10 The PWM jumper J7 is used to connect the PWM signal to either the external constant current source marke
8. d slow or the RC filter that is connected to the operational amplifier marked fast The PWM FB jumper J14 is used to select different amplification levels of the PWM signal The jumper with the battery voltage ranges are shown below J14 2 4 5V 4 5 9V 9 13V 13 18V AN101315 11 The jumper J10 is used to select between different current sense resistors The values mounted are 0 047Q and 0 100Q J10 m e ej AN101315 12 0 1000 0470 0 The different current sense voltage amplification level is selected via CURRENT jumpers J9 and J13 both jumpers must be changed in pairs see figure below www national com The upper values correspond to a current sense resistor of 0 047Q while the lower correspond to 0 100 see previous figure 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA J153 co AN101315 13 The battery voltage is selected with the Voltage jumpers J11 and J12 see below for settings Ni 4 Cells Ni 4 Cells Ni 8 Cells Ni 8 Cells Ni 6 Cells Ni 6 Cells Li 4 Cells Ni 10 Cells Li 4 Cells Ni 10 Cells Li 3 Cells Li 3 Cells Li 2 Cells Ni 5 Cells Li 2 1 Cells Ni 5 Cells Li 1 Cells J11 J12 AN101315 14 The jumper J3 is used to connect to an optional NTC resistor If no temperature sensor is used the jumper J8 must be shorted The Demo board was designed for an NTC thermistor from Siemens B57861S302F40 with the following specifications 3kQ 25
9. e 800 mAh Li lon CC minutes Li lon CV minutes Appropriate Charge Rates 3 2C 2 4C 1 4C 1 2C 0 90 0 7C 0 5C 0 4C 0 75 0 7 gt R 100kN C 47nF AN101315 18 www national com VOLL NV AN 1164 The actual timeouts with RCIN 2 5 MHz is Phase Timeout Fast Charge 330 Minutes Topping Charge EXAMPLE 2 Lilon Battery Pack Capacity 1200 mAh Charge Current 1500 mA 1500 mA Charge Rate 1200 mAh The actual timeouts with RCIN 2 5 MHz is ee OO m 1 25 8 1 2C gt R 100k C 22nF AN101315 19 Fast Charge Constant Current 130 Minutes Topping Charge Constant Voltage 190 Minutes 1 2 2 4 Setting The Charge Current The charge current is selected by setting the current sensing resistor and the gain of the differential amplification stage The current sensing resistor R5 should be dimensioned such that the voltage drop over it is not too small since the signal will be more susceptible to noise and offsets in the amplification stage The resistance should not be too large either especially in high current applications because this will only generate more heat from the component A suitable value is one where 50 mV dropped across the resistor when maximum current flows through it The differential signal is then amplified inverted and centered around the 2 5V reference by the operational amplifier and fed to the CS p
10. ging and stays in error mode until the battery is removed If the battery voltage has not risen above the bad battery threshold CEL pin lt 1 2V then the battery is considered to be defective and the charger goes into error mode If the battery passes all tests then after the five minutes have passed the charger starts the next phase Fast Charge During Fast Charge the charger applies a constant current to the battery and monitors both battery voltage and temperature The charger is looking for a drop in the battery voltage that normally occurs at the end of the Fast Charge cycle The size of the voltage drop differs depending on battery type Ni Cd Ni MH For Ni Cd it s approximately 50 mV cell and for Ni MH it s approximately 17 mV cell If the temperature rise is larger than 50 mV minute 1 C minute when charging Ni MH batteries the battery has reached the end of the Fast Charge cycle During charging the temperature inoput is constantly measured to ensure that the battery s temperature is within proper range If the temperature is out of range the charger aborts the charge and goes into error mode During the next charge phase Topping Charge the LM3647 applies a small current of 0 2C for a time set by the time selection RC network see section below This phase may be followed by a Maintenance Charge phase depending on selection pins 1 2 2 Charging Li lon Batteries The charger detects that a battery is connected
11. in on the LM3647 The gain must be dimensioned by setting the appropriate ratio between R1 R2 and R3 R4 The figure below is dimensioned for a maximum current of about 1 1A This was dimensioned using the following formula Max Current RR X Vper 1 5V R1 R2 R3 R4 R3 5 1kQ R1 100kQ R5 0 047k0 L Max Current 1 09Ampere 2 5V REFERENCE POWERSUPPLY AN101315 2 www national com 1 2 2 5 Setting Maximum Battery Voltage The resistor network see the figure below scales the battery voltage to a suitable level for the LM3647 For Ni Cd Ni MH batteries the network is less critical but limits the maximum battery voltage it is only used as a backup termination method For Li lon batteries the network must be more accurate requiring precision resistors with low tolerances For Ni Cd Ni MH The dimensioning is accomplished in the following manner First calculate the maximum battery voltage for the specific battery pack See example below Battery Voltage Cell 1 2V NumberOfCells 5 Battery PackVoltage 1 2x5 6V MaximumBatteryVoltage Cell 1 85V gt MaximumBattery Voltage 1 85x5 9 25V When the Maximum Battery Voltage has been determined the voltage divider network has to be dimensioned using the following formula RI ann MaximumBatteryVoltage x R6 R7 gt CEL 3 071V AN101315 3 BATTERY_VOLTAGE R6 CEL R7 C1 AN101315 4 e For Li lon The voltage divider network for Li lon is very importan
12. put is connected to an operational amplifier that amplifies the voltage across a current sense resistor located at the positive battery terminal The PWM output can be configured as a high speed PWM or as a low speed ON OFF output for an external current regulator The latter is for low cost Ni Cd Ni MH charger applications eliminating the need for any operational amplifiers or current feedback circuitry www national com The high speed PWM is filtered to a DC level and fed into an operational amplifier that controls a power NPN transistor The LM3467 requires charge current feedback to control the charge current 1 2 Modes of Operation 1 2 1 Charging Ni Cd Ni MH Batteries The charger detects that a battery is connected when the CEL pin gt 1 0V The charger can also detect a battery that has been deeply discharged and does not have any voltage across the battery terminals This is accomplished by applying a small pre charge current once every minute for up to 15 seconds The deeply discharged battery will accept this charge and the battery potential will eventually rise above the 1 0V limit to initiate normal charging When the charger has detected a battery CEL pin gt 1 0V it checks to see if the temperature is within range to start charging If itis then it applies a small current of 0 2C for approximately 5 minutes If the battery voltage exceeds the maximum battery voltage CEL pin gt 3 017V the LM3647 stops char
13. se failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user National Semiconductor National Semiconductor Corporation Europe Americas Fax 49 0 180 530 85 86 Tel 1 800 272 9959 Email europe support nsc com Fax 1 800 737 7018 Deutsch Tel 49 0 69 9508 6208 Email support nsc com English Tel 44 0 870 24 0 2171 www national com Fran ais Tel 33 0 1 41 91 8790 National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications 2 A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness National Semiconductor National Semiconductor Asia Pacific Customer Japan Ltd Response Group Tel 81 3 5639 7560 Tel 65 2544466 Fax 81 3 5639 7507 Fax 65 2504466 Email ap support nsc com jenuew S 49Sp ubiseg 39Uu31943Y J P9SIN DOLL NV
14. t If the battery voltage is scaled too low the battery will not attain its full capacity when charged and if scaled too high the battery may become damaged Never exceed the recommended maximum voltage or current for a Li lon battery The dimensioning is done in the following manner First calculate the maximum battery voltage for the specific battery pack See example below BatteryVoltage Cell 3 6V NumberOfCells 2 Battery PackVoltage 3 6x2 7 2V MaximumBatteryVoltage Cell 4 1V gt MaximumBattery Voltage 4 1x2 8 2V When the maximum battery voltage has been determined the voltage divider network has to be dimensioned using the following formula MaximumBatteryVoltage x 2 675V R7 R6 R7 2 740V if SEL3 is set to Vcc The LM3647 has two different regulation voltages which the user can select These are 2 675V SEL3 tied to GND and 2 740V SEL3 tied to Vec This selection pin can be used to configure the charger to regulate for different input voltages so that the charger can handle both 3 6V and 3 7V cells without changing the resistor values in the divider network SEL3 can also be used if there is problem in finding the right values in the resistor network The recommended tolerance of the resistors are 0 1 but 1 may be used with a marginal loss of battery capacity by subtracting the tolerance of the divider network from the maximum battery voltage e Using the LM3647 without current feedback
15. t Charge Constant Voltage During this phase the charger will keep the voltage constant and stay in this phase until the current has decreased to a threshold value CS at 2 3V The battery is now fully charged and the charger can behave in different modes depending on SEL1 It can either maintenance charge the battery and restart the charge process if the battery voltage drops below the maintenance restart threshold value CEL lt 2 158V or just maintenance charge the battery and don t restart the charge process if the battery becomes discharged The last mode is no maintenance charge and restarts the charge process if the battery voltage drops below the maintenance restart threshold value CEL lt 2 153V 1 2 2 1 Components Critical to Total Charger Performance e The capacitance C2 connected to CEXT must be of a type that has low internal resistance low loss high stability and low dielectric absorption The capacitance mounted on the Demo Board is a metallized polyester type from WIMA 2220 series e The operational amplifiers U1 and U2 must be capable of rail to rail output and have a high PSRR PowerSup plyRejectionRatio because they are both powered directly from the unregulated DC input U1 must also have enough current drive to control the transistor Q3 U2 should preferably have a low input offset since this error will be amplified e The regulator IC2 criteria is that it has to be able to handle the input D
16. tery without additional hardware AN 1164 Ni 4 Cells Ni 4 Cells Ni 8 Cells Ni 8 Cells Ni 6 Cells Ni 6 Cells Li 4 Cells Ni 10 Cells Li 4 Cells Ni 10 Cells Li 3 Cells Li 3 Cells Li 2 Cells Ni 5 Cells Li 2 1 Cells Ni 5 Cells Li 1 Cells J11 J12 AN101315 14 Charge Current The charge settings for LM3647 current control are shown below If the external LM317 is used to control the charge current then the jumpers J9 J10 and J13 have no relevance when using LM317 regulation mode this jumper must be placed in either position If external LM317 regulation is used then set jumper J7 to position slow for LM3647 regulation set J7 to fast LM3647 Current Regulation The jumper J10 is used to select between different current sense resistors The values available are 0 047Q and 0 100Q 0 1000 0 0470 Jio m e e AN101315 12 The charge current is set with jumpers J9 and J13 The figure shows two possible currents that depend on how jumper J10 is set The higher current is selected when J10 is set to 0 047Q and the lower current is selected when J10 is set to 0 100 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA J9 J13 AN101315 13 1 0 FUNCTIONAL DESCRIPTION 1 1 General The LM3647 has voltage and current sensing inputs that are used to control a PWlM output The voltage input is connected to the battery via a resistor divider network and the current in
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